Then the 18-year-old athlete and band standout got high on the fake pot last June and complained to a friend “that he felt like he was in hell,” his father said.

Though he had never suffered from depression, the teenager went home, found a shotgun and killed himself – one of at least nine U.S. deaths in the last year that authorities suspect were caused by synthetic products designed to mimic marijuana, cocaine and other illegal drugs.

An Associated Press analysis shows that the substances are increasingly causing users to fall seriously ill, with some suffering seizures and hallucinations.

Available in many head shops for as little as $10, the synthetic drugs are often packaged as incense or bath salts, but they do nothing to perfume the air or soften water.

As more Americans experiment with them, the results are becoming evident at hospitals: a sharp spike in the number of users who show up with problems ranging from labored breathing and rapid heartbeats to extreme paranoia and delusions. The symptoms can persist for days.

“These kids weren’t looking for anything bad to happen,” Mike Rozga said of his son’s death. “The truth is they didn’t know what they had gotten themselves into.”

At the request of the AP, the American Association of Poison Control Centers analyzed nationwide figures on calls related to synthetic drugs. The findings showed an alarming increase in the number of people seeking medical attention.

At least 2,700 people have fallen ill since January, compared with fewer than 3,200 cases in all of 2010. At that pace, medical emergencies related to synthetic drugs could go up nearly fivefold by the end of the year.

“Many of the users describe extreme paranoia,” said Dr. Mark Ryan, director of the Louisiana Poison Center. “The recurring theme is monsters, demons and aliens. A lot of them had suicidal thoughts.”

The recent surge in activity has not gone unnoticed by law enforcement and elected officials.

The Drug Enforcement Administration recently used emergency powers to outlaw five chemicals found in synthetic pot, placing them in the same category as heroin and cocaine.

But manufacturers are quick to adapt, often cranking out new formulas that are only a single molecule apart from the illegal ones.

On Wednesday, the Senate’s Caucus on International Narcotics Control held a hearing in Washington to discuss curbing the growth of synthetics.

“This is a whole new method of trafficking,” testified Joseph T. Ranznazzisi, deputy assistant administrator in the DEA’s office of diversion control. “We’ve never experienced this before, when the product is just on the shelf.”

Rozga implored lawmakers to act swiftly to prevent more deaths: “We are not doing enough, and we are not moving quickly enough.”

Recreational drugs created in the laboratory have been around at least since the middle of the 20th century, when LSD was first studied. But these latest examples emerged only a few years ago, starting in Europe.

The products were typically made in China, India and other Asian nations and soon arrived in Britain and Germany, according to DEA spokesman Rusty Payne.

In the United States, fake marijuana was last year’s big seller, marketed under brands such as “K2″ or “Spice.” This year, the trend is “bath salts” with names like “Purple Wave” and “Bliss.”

Besides being cheap and easily obtained, they do not show up in common drug tests.

Synthetic marijuana typically involves dried plant material sprayed with one of several chemical compounds, most of which were created by a Clemson University scientist for research purposes in the 1990s. The compounds were never tested on humans.

It’s packaged to look like pot, and users typically smoke it, but experts say the high is more comparable to cocaine or LSD.

The bath salts are crystalized chemicals that are snorted, swallowed or smoked. They contain two powerful stimulants: methylenedioxypyrovalerone (or MDPV) and mephedrone, which mimic cocaine, LSD and methamphetamine.

So far in 2011, poison control centers have received nearly 1,300 calls about synthetic pot, compared with 2,874 calls for all of last year, according to the poison control center data.

Poison calls for bath salts rose at an even greater rate. The centers took 301 calls in all of 2010, but had more than 1,400 for the first three months of 2011. Most of the calls came from doctors and nurses reporting patients in emergency rooms.

“The problem is really exploding here,” said Dr. Elizabeth Scharman, director of the West Virginia Poison Center. Her state had three cases of bath-salt poisoning in December.

“We’ve had 131 cases since Jan. 1,” and one-third of those were within the past two weeks, she said late last month. A law banning bath salts and synthetic marijuana was signed Tuesday by acting Gov. Earl Ray Tomblin.

Physicians generally treat the overdoses with anti-anxiety medication such as Valium and Xanax, which ease the frenetic, drug-fueled activity in the brain and body.

“They cut back on the hallucinations, slow the heart rate, lower the blood pressure. It can take large doses. It can take repeated doses,” Scharman said.

In some patients, symptoms can last for days.

“One described it as like being on cocaine, but 10 times worse,” said Anna Rouse Dulaney of the Carolinas Poison Center in Charlotte, N.C.

DEA agent Gary Boggs said users assume that the products are safe because they are available in stores, even though they are typically labeled “not for human consumption.”

“These products are in an unregulated, unlicensed industry,” Boggs said. “No one knows the strength of the ingredients. You don’t know what you’re taking.”

In addition to the DEA’s recently adopted ban, a federal law allows for prosecution of “analogue” drugs that mimic the effects of illegal substances.

But authorities acknowledge the challenge of stopping the drugs’ spread. DEA experts are evaluating as many as 50 new synthetics.

At least 20 states have banned chemicals found in fake marijuana, according to a report from the National Conference of State Legislatures compiled for the AP. Most others have legislation pending.

At least nine states have banned substances found in bath salts, and 25 have laws in the works.

Lawmakers know they’re fighting an uphill battle.

“These chemists are pretty sophisticated and creative and are going to stay one step ahead of us, I’m afraid,” said Kentucky state Rep. John Tilley, a Democrat who sponsored his state’s ban on drug-infused bath salts.

Some head shop owners see all the alarm as an overreaction.

In Des Moines, Iowa, near Drake University, the Day Dreams shop has found the synthetic marijuana “Spice” to be a proven money-maker. Along with incense, hippie clothing and drug paraphernalia, the store has sold thousands of packets of the crumbly, brownish-green leaves. Many of the packages are displayed behind the counter as a safeguard against shoplifting.

Contrary to DEA claims that the product is most popular among teens and college-age customers, co-owner Kathy Fiedler said two-thirds of her buyers are middle-aged.

“I even have grandmothers coming in,” said Fiedler, 56.

If Iowa lawmakers adopt a ban, she said, they risk opening the door to shady backroom chemists crafting far more dangerous things.

Reports of misuse are widespread.

In Kentucky, authorities say a young woman driving on a highway after using bath salts became convinced her 2-year-old was a demon. She allegedly stopped the car and dropped the child on his head. He survived and was taken from his mother’s custody.

A Hawaii man pleaded guilty to attacking his girlfriend and trying to throw her off an 11th-floor balcony while high on “Spice.”

In January, a Fulton, Miss., man who hallucinated after taking bath salts used a hunting knife to slit his face and stomach.

And in March, a 19-year-old man named Trevor Robinson-Davis died in suburban Minneapolis after overdosing at a party on a synthetic drug called 2C-E, a “cousin” to a banned rave-party drug. Ten others at the party became ill.

Back in Indianola, David Rozga’s parents said their son had been active in his church and was preparing to start college in the fall. He loved the Green Bay Packers so much he had Brett Favre’s No. 4 tattooed on his shoulder.

“We said at the time, `If this was the worst thing he ever did, we did a pretty good job.’ Unfortunately, it wasn’t,” Mike Rozga said.

Sen. Charles Grassley, an Iowa Republican, introduced a measure bearing the younger Rozga’s name that would permanently ban five chemicals used in synthetic marijuana products.

Jan Rozga hopes the law will be her son’s legacy.

“I did not stop being David’s mother when he died,” she said. “I still feel very protective over him, what happened to him, and I want to right that wrong for him.”